Significant progress has been made in the understanding of the neurobiological abnormalities associated with depression and bipolar disorders. However, the specific sites of such abnormalities in these disorders are still unclear. Several studies indicate increased 5HT2A receptors and 5HT2A receptor linked phosphoinositide (PI) signaling activity in the brain and platelets of patients with mood disorder. The studies in the previous funding period, indicated that 5HT2A receptors and IP3 receptors are increased in the platelets of unipolar patients, PKC activity, PLC activity and selective isozymes of PKC and PLC are decreased and MARCKS, a substrate for PKC increased in the platelets of bipolar patients. In the proposed research, the main objective is to extend our findings and to study further downstream events in the PI signaling system, such as: PKC substrates and transcription factors in the platelets and neutrophils obtained in drug-free unipolar and bipolar patients. More specifically, we will study PKC, MARKCS and GAP43 the substrates for PKC, in the platelets of unipolar and bipolar patients, DNA binding activity of transcription factors AP-1, GRE, DNA binding activity, protein expression and mRNA levels of another transcription factor CREB in the neutrophils of unipolar and bipolar patients. In addition, we will study the activity, protein level and mRNA levels of GSK-3B and protein levels of B-catenin, the two important components of the WNT pathway that appears to be related to and may be regulated by PKC and has been implicated to be abnormal in bipolar disorders. Our proposed studies are based on our central hypothesis that an abnormal PT signaling system in patients with mood disorders is associated with abnormality of several of its components leading to abnormality of transcription factors and gene expression.These studies will enhance our understanding of the involvement of transcription factors and PKC substrates in the pathophysiology of unipolar and bipolar disorders and may indicate if they may be possible sites for therapeutic action of antidepressants and mood stabilizing drugs, thus, may result in more appropriate and better treatment these disorders.